PDI fuel system monitor

Abstract

A fuel delivery system for a vehicle having an engine configured to selectively operate between a port fuel injection (PFI) mode, a gasoline direct injection (GDI) mode, and a port and direct fuel injection (PDI) mode. The fuel delivery system includes a PFI system including a plurality of PFI injectors configured to supply fuel to the engine during a PFI mode, and a GDI system including a plurality of GDI injectors configured to supply fuel to the engine during a GDI mode. The fuel system monitor is configured to monitor the fuel delivery system when operating in a PFI mode and to attribut any fuel delivery system failure occurring during the PFI mode to the PFI system only, and to monitor the fuel delivery system when operating in a GDI mode and to attribut any fuel delivery system failure occurring during the GDI mode to the PFI system only. And attributing any fuel supply system failure occurring during the GDI mode to the GDI system only.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of U.S. Nonprovisional Application No. 17 / 880,969, filed on August 4, 2022. The disclosure of that application is incorporated herein by reference in its entirety. Technical Field

[0003] The present application relates generally to internal combustion engines and, more particularly, to a fuel system monitor for an engine having a port and direct fuel injection system. Background Art

[0004] Traditionally, internal combustion engines have used port fuel injection (PFI) fuel delivery technology. PFI engines mix fuel and air in the intake port and then draw the mixture into the engine cylinders for combustion. This mixing is performed to optimize combustion and improve engine performance. More recently, gasoline direct injection (GDI) fuel delivery technology has been introduced to provide improved fuel economy. GDI engines draw air into the cylinder during the intake stroke and inject fuel directly into the cylinder to mix with the air during the intake or compression stroke. This mixing method potentially provides improved fuel economy and engine performance under various load conditions. However, both PFI and GDI engines have their unique advantages and disadvantages when compared to each other.

[0005] In an attempt to take advantage of the benefits of both systems, some engines include both port and direct fuel injection (PDI) fuel delivery systems. However, conventional monitoring systems are not able to pinpoint system-specific faults (i.e., whether the fault is in the PFI system or the GDI system) and may potentially erroneously pass through a faulty system (e.g., a PFI system fault but passed through under GDI operation). Thus, while such systems do perform well for their intended purpose, it is desirable to provide continued improvements in the related art. Summary of the invention

[0006] According to an exemplary aspect of the present invention, a fuel delivery system for a vehicle is provided, the vehicle having an engine configured to selectively operate between a port fuel injection (PFI) mode, a gasoline direct injection (GDI) mode, and a port and direct fuel injection (PDI) mode. In an exemplary embodiment, the fuel delivery system includes a PFI system and a GDI system, the PFI system including a plurality of PFI injectors configured to supply fuel to the engine during the PFI mode, and the GDI system including a plurality of GDI injectors configured to supply fuel to the engine during the GDI mode. A fuel system monitor is configured to monitor the fuel delivery system when operating in the PFI mode and attribute any fuel delivery system fault occurring during the PFI mode only to the PFI system, and to monitor the fuel delivery system when operating in the GDI mode and attribute any fuel delivery system fault occurring during the GDI mode only to the GDI system.

[0007] In addition to the above, the fuel delivery system may include one or more of the following features: wherein the fuel system monitor is further configured to monitor the fuel delivery system when operating in PDI mode and classify any fuel delivery system faults occurring during PDI mode as conventional fuel system faults; wherein the fuel delivery system includes a service procedure to determine whether a conventional fuel system fault is caused by the PFI system or the GDI system; wherein the service procedure includes providing a technician with the ability to select to force the engine to operate in either PFI mode or GDI mode.

[0008] In addition to the above, the fuel delivery system may include one or more of the following features: wherein the fuel system monitor includes a first monitor that monitors the fuel delivery system only in PFI mode, a second monitor that monitors the fuel delivery system only in GDI mode, and a third monitor that monitors the fuel delivery system only in PDI mode; wherein the first monitor, the second monitor, and the third monitor are separate monitors; wherein the fuel system monitor is configured to set a PFI-specific diagnostic trouble code (DTC) or a generic DTC accompanied by a PFI-specific service flag when a fuel delivery system fault occurs while operating in PFI mode; and wherein the fuel system monitor is configured to set a GDI-specific diagnostic trouble code (DTC) or a generic DTC accompanied by a GDI-specific service flag when a fuel delivery system fault occurs while operating in GDI mode.

[0009] In addition to the above, the fuel delivery system may include one or more of the following features: wherein the fuel system monitor is configured to set a general fault when a fuel delivery system fault occurs when operating in PDI mode; wherein the fuel delivery system fault is an air-fuel ratio error; wherein the fuel delivery system fault indicates that the fuel delivery system is operating in a too lean or too rich manner; and wherein the fuel system monitor is configured to monitor a short-term fuel trim (STFT) and a long-term fuel trim (LTFT) to determine whether a fuel delivery system fault occurs during PFI mode, GDI mode, or PDI mode.

[0010] According to another exemplary aspect of the present invention, a method for monitoring a fuel delivery system of a vehicle is provided, the vehicle having an engine with a fuel system monitor, a port fuel injection (PFI) system, and a gasoline direct injection (GDI) system, the engine being configured to selectively operate between a PFI mode, a GDI mode, and a port and direct fuel injection (PDI) mode. In an exemplary embodiment, the method includes: when operating in the PFI mode, monitoring the fuel delivery system via the fuel system monitor, and attributing any fuel delivery system faults that occur during the PFI mode to the PFI system only, and when operating in the GDI mode, monitoring the fuel delivery system via the fuel system monitor, and attributing any fuel delivery system faults that occur during the GDI mode to the GDI system only.

[0011] In addition to the above, the method may include one or more of the following features: when operating in PDI mode, monitoring the fuel delivery system via a fuel system monitor, and classifying any fuel delivery system fault occurring during the PDI mode as a conventional fuel system fault; wherein the fuel system monitor includes a first monitor that monitors the fuel delivery system only in PFI mode, a second monitor that monitors the fuel delivery system only in GDI mode, and a third monitor that monitors the fuel delivery system only in PDI mode; and when a fuel delivery system fault occurs when operating in PFI mode, setting a PFI-specific diagnostic trouble code (DTC) or a generic DTC accompanied by a PFI-specific service flag, when a fuel delivery system fault occurs when operating in GDI mode, setting a GDI-specific DTC or a generic DTC accompanied by a GDI-specific service flag, and when a fuel supply system fault occurs when operating in PDI mode, setting a conventional fault.

[0012] In addition to the above, the method may include one or more of the following features: wherein the fuel delivery system fault is an air-fuel ratio error, the fuel delivery system fault indicating that the fuel delivery system is operating in a too lean or too rich manner; and using a fuel system monitor to monitor a short-term fuel adjustment (STFT) and a long-term fuel adjustment (LTFT) to determine whether the fuel delivery system fault occurs during PFI mode, GDI mode or PDI mode.

[0013] Other areas of applicability of the teachings of the present disclosure will become apparent from the detailed description, claims, and drawings provided below, wherein like reference numerals represent like features in the several views of the drawings. It should be understood that the detailed description including the disclosed embodiments and the figure references therein are merely exemplary in nature and are used only for illustrative purposes and are not intended to limit the scope of the present disclosure, its application, or use. Therefore, variations that do not depart from the gist of the present disclosure are intended to be within the scope of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 is a schematic diagram of an engine and fuel delivery system according to the principles of the present disclosure; and

[0015] Figure 2 The monitoring and control according to the principles of the present disclosure is shown Figure 1 An example method of a fuel delivery system is shown. DETAILED DESCRIPTION

[0016] The present application generally relates to a monitoring system and method for a fuel delivery system for an engine equipped with a port and direct fuel injection (PDI) system, the monitoring system being configured to selectively operate between a port fuel injection (PFI) mode, a gasoline direct injection (GDI) mode, or a combination of the two (PDI mode). The fuel delivery system changes the operating mode to take advantage of the advantages of PFI and GDI systems, for example, to reduce emissions and / or improve fuel economy. Advantages of a GDI system include charge cooling / knock mitigation, combustion stability (EGR), ignition / spark retard authority, combustion duration reduction, and multiple injection events. Advantages of a PFI system include fuel / air vaporization time (cold), reduced intake / valve deposits, reduced particulate matter, reduced oil dilution risk, and quieter operation.

[0017] In an example embodiment, the PDI fuel system monitor is a diagnostic strategy with an engine control unit (ECU) that allows the fuel system monitor to find out whether the air-fuel ratio error comes from the PFI injection system or the GDI injection system. The PDI fuel system monitor uses short-term and long-term fuel adjustments to determine whether there is a lean or rich fault. In one example, the short-term fuel adjustment (STFT) is an instantaneous correction to the amount of fuel delivered to the engine based on an error as indicated by one or more O2 sensors. The long-term fuel adjustment (LTFT) is a cumulative correction to the amount of fuel delivered to the engine. The LTFT can also be called a volumetric efficiency correction, which describes a correction to the airflow estimation model. The LTFT and STFT work together to ensure that the error in the amount of fuel delivered to the engine is minimized. The sum of the LTFT and STFT represents the total fuel adjustment, or the total system richness or leanness.

[0018] During operation, there are engine speeds / loads where the engine will operate with only the PFI system, only the GDI system, or a combination of the PFI system and the GDI system. As such, the PDI fuel system monitor includes three different monitoring modes that are selectively used based on the fuel mode of the PDI-equipped engine.

[0019] If the engine is operated in PFI-only mode, the fuel system monitor will attribute any fuel system malfunction to the PFI system only, either by setting a DTC specific to the PFI system or by setting a generic DTC accompanied by a service flag specific to the PFI system. Similarly, if the engine is operated in GDI-only mode, the fuel system monitor will attribute any fuel system malfunction to the GDI system only, either by setting a DTC specific to the GDI system or by setting a generic DTC accompanied by a service flag specific to the GDI system. When operating in PDI mode using both the PFI and GDI systems, the fuel system monitor will set any fuel system malfunction to a generic fuel system DTC, regardless of configuration.

[0020] In one aspect, if a general fault is set without an accompanying DTC or service flag specific to PFI or GDI, the system is configured with a service procedure to find out if the general fault is caused by one specific system. The service procedure will allow the technician to select the fuel mode (PFI or GDI) in which the vehicle is operating. Once the vehicle is operating in full DI or PFI mode, the technician can use the resulting fuel adjustments to find out which system is causing the problem. In one example, the problematic system is identified as showing a significantly larger fuel adjustment than the other system(s).

[0021] In an exemplary embodiment, the PDI fuel system monitor can be configured in one of two ways. The first configuration sets separate specific diagnostic trouble codes (DTCs) for PFI, GDI, and general faults. The second configuration sets a generic DTC that is configured with an accompanying service flag specific to the PFI or GDI system.

[0022] For the first configuration, the fuel system monitor can only clear a PFI specific, DI specific, or generic fuel system DTC if the fuel system monitor is passed while operating in the same fuel mode that set the specific DTC (i.e., the system must be passed in PFI mode to clear a PFI specific DTC). For the second configuration, the fuel system monitor can clear a fuel system monitor fault if the accompanying service flag(s) have also been cleared. The PFI service flag and the GDI service flag can only be cleared when operating in their respective modes.

[0023] First reference Figure 1 , an exemplary internal combustion engine for a vehicle is shown and generally designated by reference number 10 . Internal combustion engine 10 generally includes an intake system 12 , a fuel delivery system 14 , and an exhaust system 16 .

[0024] The engine 10 also includes a cylinder head and cylinder block 20 that define one or more cylinders 22, each housing a reciprocating piston (not shown). Air and fuel are supplied to combustion chambers 24 of the cylinders 22 via the intake system 12 and the fuel delivery system 14, respectively. The air / fuel mixture is ignited in the combustion chamber 24, and the resulting combustion gases are directed from the combustion chamber 24 to the exhaust system 16.

[0025] The intake system 12 generally includes an air filter 26, a throttle control valve 28, and an intake manifold 30. Air enters the vehicle through an intake port 32 and is filtered in the air filter 26 before being delivered to intake passages 34 of the cylinders 22 for combustion therein.

[0026] In the exemplary embodiment, the fuel delivery system 14 generally includes a low-pressure fuel pump 36, a port fuel injection (PFI) fuel system 38, and a gasoline direct injection (GDI) fuel system 40. The PFI fuel system 38 includes a PFI fuel pressure rail 42 and a plurality of PFI injectors 60, and the GDI fuel system 40 includes a GDI fuel pressure rail 44, a plurality of GDI injectors 62, a first deactivation GDI fuel pump assembly 46, and a second deactivation GDI fuel pump assembly 48. In the exemplary embodiment, the engine 10 includes a three-function fuel delivery system 14 that is configured to be controlled by an engine control unit (ECU) 50 to selectively operate between a PFI mode, a GDI mode, or a combination of the two (PDI mode), as described in more detail herein. Generally, during low engine load conditions or when intake air motion is low, the engine operates in PFI mode, during high engine load conditions or when intake air motion is high, the engine operates in GDI mode, and under other speed / load conditions, the engine operates in PDI mode.

[0027] The low pressure fuel pump 36 is disposed within the fuel tank 52 and is configured to supply fuel from the fuel tank 52 to a main fuel delivery line 54. As shown, the main fuel delivery line 54 supplies fuel to a PFI fuel delivery line 56 and a GDI fuel delivery line 58. The PFI fuel delivery line 56 is fluidly coupled to the PFI fuel pressure rail 42 to supply fuel to the PFI injectors 60. In the exemplary embodiment, the PFI injectors 60 are configured to supply fuel to the intake passage 34 where the fuel is mixed with air from the intake system 12 before being supplied to the combustion chamber 24.

[0028] GDI fuel delivery line 58 is fluidly coupled to GDI fuel pressure rail 44 to supply fuel to GDI injectors 62. In the exemplary embodiment, GDI injectors 62 are configured to supply fuel directly to cylinders 22 where the fuel mixes with air from intake system 12 and combusts. Figure 1 As shown, the GDI fuel delivery line 58 is divided into a first GDI fuel supply line 64 and a second GDI fuel supply line 66 for supply. Each of the first fuel supply line 64 and the second fuel supply line 66 is fluidly coupled to the GDI fuel pressure rail 44 so that when high output is required to meet peak engine power or torque requirements, an increased fuel supply can be provided to the GDI injectors 62. In one example, the first GDI fuel supply line 64 supplies a portion (e.g., three) of the GDI injectors 62, while the second GDI fuel supply line 66 supplies another portion (e.g., the remaining three) of the GDI injectors 62. However, in embodiments having only a single deactivated GDI pump assembly 46, 48, all of the GDI injectors 62 are supplied by the assembly 46 or 48.

[0029] The GDI fuel pump assemblies 46, 48 are disposed on the GDI fuel supply lines 64, 66 and are configured to be controlled by the ECU 50 (or other controller) to selectively operate between an enabled mode and a disabled mode. As used herein, the term controller refers to an application specific integrated circuit (ASIC), electronic circuit, processor (shared processor, dedicated processor or processor group) and memory executing one or more software or firmware programs, combinational logic circuits and / or other suitable components that provide the described functionality.

[0030] Continue to refer Figure 1 The engine 10 equipped with PFI operation capability, GDI operation capability, and PDI operation capability is configured to operate in various modes to selectively improve vehicle emissions, fuel economy, and / or engine power output. To identify any faults in the fuel delivery system 14, the engine 10 includes a PDI fuel system monitor 70, which may include one or more controllers or modules. The PDI fuel system monitor 70 is in signal communication with the ECU 50, which is also in signal communication with one or more O2 sensors 72 located in the exhaust system 16.

[0031] In an exemplary embodiment, the PDI fuel system monitor 70 is configured for the identification of PFI and GDI specific faults. Specifically, the PDI fuel system monitor 70 is divided into three discrete or separate monitors (70a, 70b, 70c), which can be three separate controllers / modules or part of a single controller / module. The first monitor 70a is specifically used for PFI mode operation, the second monitor 70b is specifically used for GDI mode operation, and the third monitor 70c is specifically used for PDI mode operation. Each monitor 70 is enabled when its respective fuel mode is commanded, and each monitor has its own pass / fail timer or counter (for example, so as to prevent the pass timer / counter for GDI faults from incrementing in PFI mode). The separate monitors have similar condition windows and can set PFI / GDI / conventional faults at the same time. PFI mode faults and GDI mode faults each include system-specific P codes that indicate whether the fuel delivery system 14 is too lean or too rich in this mode.

[0032] In an exemplary embodiment, the first monitor 70a is configured to set a PFI-specific DTC or flag when operating in PFI-only mode, and the second monitor 70b is configured to set a GDI-specific DTC or flag when operating in GDI-only mode. The third monitor 70c is configured to set a general fault DTC in PDI mode. If a general fault DTC is set without an accompanying system-specific DTC or flag, a subsequent service procedure can be performed to allow a technician to find out which system (PFI or GDI) caused the problem. In one example, a technician can set the fuel mode to full PFI or full DI in order to view the resulting fuel adjustments and identify which system has failed.

[0033] Reference now Figure 2 , a flow chart of an example PDI fuel system monitor control method 200 according to the principles of the present disclosure is shown. At 202, the PDI fuel system monitor 70 determines the PDI split ratio of the fuel delivery system 14. In one example, the split ratio is the fuel mass injection ratio of the GDI injector to the PFI injector. For example, a split ratio of 0.5 means that the GDI injector delivers 50% of the fuel and the other 50% of the fuel is delivered by the PFI injector. At step 204, based on the determined PDI split ratio, the PDI fuel system monitor 70 determines whether the fuel delivery system 14 is operating in PFI mode, GDI mode, or PDI mode.

[0034] If the fuel delivery system 14 is operating in the PFI mode, then in step 210, the PDI fuel system monitor 70 enables the first monitor 70a (PFI mode monitor). In step 212, the first monitor 70a monitors the LTFT and STFT (e.g., total fuel trim) of the fuel delivery system 14 to determine if a lean or rich fault is present. In step 214, the first monitor 70a determines if the determined fuel trim (e.g., total fuel trim) is greater than a calibratable predetermined fault threshold. If not, control returns to step 202. If so, in step 216, the first monitor 70a sets a PFI specific DTC or a generic DTC accompanied by a PFI specific service flag (e.g., indicating a rich condition or a lean condition). Control then ends in step 250 and may return to step 204 for another cycle.

[0035] If the fuel delivery system 14 is operating in the GDI mode, then in step 220, the PDI fuel system monitor 70 enables the second monitor 70b (GDI mode monitor). In step 222, the second monitor 70b monitors the LTFT and STFT (e.g., total fuel trim) of the fuel delivery system 14 to determine if a lean or rich fault is present. In step 224, the second monitor 70b determines if the determined fuel trim (e.g., total fuel trim) is greater than a calibratable predetermined fault threshold. If not, control returns to step 202. If so, in step 226, the second monitor 70b sets a GDI specific DTC or a generic DTC accompanied by a GDI specific service flag (e.g., indicating a rich condition or a lean condition). Control then ends in step 250 and may return to step 204 for another loop.

[0036] If the fuel delivery system 14 is operating in the PDI mode, then in step 230, the PDI fuel system monitor enables the third monitor 70c (PDI mode monitor). In step 232, the third monitor 70c monitors the LTFT and STFT (e.g., total fuel trim) of the fuel delivery system 14 to determine if a lean or rich fault is present. In step 234, the third monitor 70c determines if the determined fuel trim (e.g., total fuel trim) is greater than a calibratable predetermined fault threshold. If not, control returns to step 202. If so, in step 236, the third monitor 70c sets a general fault without an accompanying PFI or GDI specific DTC or service flag. Control then ends in step 250 and may return to step 204 for another cycle.

[0037] Described herein are systems and methods for a fuel delivery system for an internal combustion engine. The engine and fuel delivery system are configured to selectively operate between a PFI mode, a GDI mode, and a PDI mode. The PDI fuel system monitoring strategy is configured to identify whether a GDI or PFI system is faulty based on the fuel mode. There will be PFI or GDI specific DTCs or flags to indicate which system is causing the problem, which can only be cleared when operating in these specific fuel modes. If a fuel system fault is detected while operating in PDI mode, it is set to a general fault, and if no conclusion can be drawn from the existing DTCs or flags, a service procedure can be performed to pinpoint the faulty system.

[0038] It should be understood that the term "controller" as used herein refers to any suitable control device or a group of multiple control devices that are configured to perform at least a portion of the technology of the present application. Non-limiting examples include an application specific integrated circuit (ASIC), one or more processors, and non-transitory memory having instructions stored thereon, which, when executed by one or more processors, cause the controller to perform a set of operations corresponding to at least a portion of the technology of the present application. The one or more processors may be a single processor, or may be two or more processors running in a parallel or distributed architecture.

[0039] It should be understood that the mixing and matching of features, elements and / or functions between various examples may be explicitly considered herein so that those skilled in the art will understand from the present teachings that, unless otherwise described above, the features, elements and / or functions of one example may be appropriately incorporated into another example.

Claims

1. A fuel delivery system for a vehicle having an engine configured to selectively operate between a port fuel injection (PFI) mode, a gasoline direct injection (GDI) mode, and a port and direct fuel injection (PDI) mode, the fuel delivery system comprising: a PFI system comprising a plurality of PFI injectors configured to supply fuel to the engine during the PFI mode; a GDI system comprising a plurality of GDI injectors configured to supply fuel to the engine during the GDI mode; as well as A fuel system monitor, the fuel system monitor being configured to: monitoring the fuel delivery system while operating in the PFI mode and attributing any fuel delivery system fault occurring during the PFI mode solely to the PFI system; as well as The fuel delivery system is monitored while operating in the GDI mode, and any fuel delivery system faults occurring during the GDI mode are attributed solely to the GDI system.

2. The fuel delivery system according to claim 1, wherein: The fuel system monitor is further configured to monitor the fuel delivery system while operating in the PDI mode and classify any fuel delivery system faults occurring during the PDI mode as normal fuel system faults.

3. The fuel delivery system according to claim 2, wherein: The fuel delivery system includes a service procedure to determine whether the conventional fuel system malfunction is caused by the PFI system or the GDI system.

4. The fuel delivery system according to claim 3, wherein: The service procedure includes providing a technician with the ability to select to force the engine to operate in the PFI mode or the GDI mode.

5. The fuel delivery system according to claim 2, wherein: The fuel system monitor includes a first monitor that monitors the fuel delivery system only in the PFI mode, a second monitor that monitors the fuel delivery system only in the GDI mode, and a third monitor that monitors the fuel delivery system only in the PDI mode.

6. The fuel delivery system according to claim 5, wherein: The first monitor, the second monitor, and the third monitor are separate monitors.

7. The fuel delivery system of claim 2, wherein: The fuel system monitor is configured to set a PFI specific diagnostic trouble code (DTC) or a generic DTC accompanied by a PFI specific service flag when a fuel delivery system fault occurs while operating in the PFI mode.

8. The fuel delivery system of claim 2, wherein: The fuel system monitor is configured to set a GDI specific diagnostic trouble code (DTC) or a generic DTC accompanied by a GDI specific service flag when a fuel delivery system fault occurs while operating in the GDI mode.

9. The fuel delivery system of claim 2, wherein: The fuel system monitor is configured to set a general fault when a fuel delivery system fault occurs while operating in the PDI mode.

10. The fuel delivery system of claim 1, wherein: The fuel delivery system fault is an air-fuel ratio error.

11. The fuel delivery system of claim 1, wherein: The fuel delivery system fault indicates that the fuel delivery system is operating in a too lean or too rich manner.

12. The fuel delivery system of claim 2, wherein: The fuel system monitor is configured to monitor a short term fuel trim (STFT) and a long term fuel trim (LTFT) to determine if a malfunction occurs in the fuel delivery system during the PFI mode, the GDI mode, or the PDI mode.

13. A method of monitoring a fuel delivery system of a vehicle, the vehicle having an engine with a fuel system monitor, a port fuel injection (PFI) system, and a gasoline direct injection (GDI) system, the engine being configured to selectively operate between a PFI mode, a GDI mode, and a port and direct fuel injection (PDI) mode, the method comprising: while operating in the PFI mode, monitoring the fuel delivery system via the fuel system monitor and attributing any fuel delivery system fault occurring during the PFI mode solely to the PFI system; as well as While operating in the GDI mode, the fuel delivery system is monitored via the fuel system monitor and any fuel delivery system faults occurring during the GDI mode are attributed solely to the GDI system.

14. The method according to claim 13, further comprising: While operating in the PDI mode, the fuel delivery system is monitored via the fuel system monitor and any fuel delivery system faults occurring during the PDI mode are classified as normal fuel system faults.

15. The method according to claim 13, wherein: The fuel system monitor includes a first monitor that monitors the fuel delivery system only in the PFI mode, a second monitor that monitors the fuel delivery system only in the GDI mode, and a third monitor that monitors the fuel delivery system only in the PDI mode.

16. The method according to claim 13, further comprising: When a fuel delivery system fault occurs while operating in the PFI mode, a PFI specific diagnostic trouble code (DTC) or a generic DTC accompanied by a PFI specific service flag is set; When a fuel delivery system fault occurs while operating in the GDI mode, a GDI specific DTC or a generic DTC accompanied by a GDI specific service flag is set; as well as When a fuel delivery system fault occurs while operating in the PDI mode, a general fault is set.

17. The method according to claim 13, wherein: The fuel delivery system fault is an air-fuel ratio error, the fuel delivery system fault indicating that the fuel delivery system is operating in a too lean or too rich manner.

18. The method of claim 13 further comprising monitoring a short term fuel trim (STFT) and a long term fuel trim (LTFT) with the fuel system monitor to determine if the fuel delivery system fault occurs during the PFI mode, the GDI mode, or the PDI mode.

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